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GlobalInvacom adds DTT to

its Fibre Optic System

•addsterrestrialsignalstofibreopticdistributionsystem•excellentperformancewithnearlynodegraditioninsignalquality•transmitsterrrestrialfrequencieswithveryflatcharacteristics•perfectsolutiontodistributeterrestrialandsatellitesignalsoveragreatdistance•suitableforallkindsandtypesofterrestrialsignals

TEST REPORT Fibre Optic DTT

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01-02/2013

www.TELE-audiovision.com/13/01/globalinvacomGTU

54 55TELE-audiovision International — The World‘s Largest Digital TV Trade Magazine — 01-02/2013 — www.TELE-audiovision.com www.TELE-audiovision.com — 01-02/2013 — TELE-audiovision International — 全球发行量最大的数字电视杂志

GlobalInvacom GTU QUAD And GTU QUATRO

Optical to RF Converters

TEST REPORT Fibre Optic DTT

GlobalInvacom is the very well known company in the field of fiber optics re-ception systems, consisting of the Glo-balInvacom fibre optic LNBs and the corresponding distribution accessories, as fibre optic converters, cables and splitters. TELE-satellite has published a number of test reports dedicated to their products. However, up to now, we were focusing on the satellite TV signal distribution using GlobalInvacom’s fibre optic system and ignoring terrestrial TV signals. But nowadays a contemporary TV installation requires both kinds of digital TV signals: satellite and terres-trial. GlobalInvacom even has the right products for this as well! So we set out to give their new DTT enhanced compo-nents a closer look.

For our test, we used the FibreIRS ODU32 optical transmitter you al-ready know from our previous reports - our latest test report was published in TELE-satellite 09-10/2012. The new unit, except for accepting the signal from an optical LNB, also allows you to connect DTT/DAB/FM signals from a terrestrial antenna. By writing DTT we mean any standard of terrestrial signal - not only DVB-T or DVB-T2 but as well ATSC, DMBT or ISDB-T - anything in the regular VHF/UHF and FM range. All those signals are converted to light and you can then distribute them in large buildings or wherever you want. But at the other end of an optical fiber net-work you need a complimentary part: a light-to-RF converter. Instead of testing the already known MDU device we de-cided to take a closer look at the brand new FibreIRS GTU devices. There are two variants of them: QUAD GTU and QUATRO GTU.

Each GTU device is hidden in a black plastic enclosure. You are supposed to mount the plastic back plate on the wall or other flat surface and it should be mounted indoors in a dry environment. The main device (QUAD or QUATRO

TELE-audiovision Test Editor Jacek Pawlowski testing the new GTUs from GlobalInvacom

Global Invacom QUAD GTU and QUATRO GTU

Perfect solution for loss-less distribution of satellite and terrestrial TV and Radio

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56 TELE-audiovision International — The World‘s Largest Digital TV Trade Magazine — 01-02/2013 — www.TELE-audiovision.com

converter) is then clicked into place on the back plate. Now comes the time for con-necting cables. As could be expected, the GTU device has one optical input with a FC-PC connector.

The QUAD GTU converter has four equivalent outputs.

You can connect a suitable triplex (TV, satellite, Radio) wall outlet to each of them. Then, to each socket you can connect a satellite re-ceiver, a TV-set orDAB ra-dio and a FM radio. In other words, the terrestrial band is combined with the satel-

lite IF signal in each output and all you need is a suit-able socket to split them for terminal devices.

The QUATRO GTU has five outputs: VL, HL, VH, HH and DTT/DAB. In this case the terrestrial band is separated from the satellite IF signals.

The idea here is to connect a suitable multiswitch, which is then fed into satellite re-ceivers. The DTT/DAB out-put would go directly into a TV-set or DAB/FM radio.

Each GTU unit has an ad-ditional DC power socket. This power supply is re-

Jacek Pawlowski taking notes of the measurements

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Channel Number Center Frequency Channel Bandwidth DVB-T Modulation Parameters

MHz MHz41 634 8 8k 64QAM 1/8 3/445 666 8 8k 64QAM 1/4 5/648 690 8 8k 64QAM 1/8 3/4

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58 TELE-audiovision International — The World‘s Largest Digital TV Trade Magazine — 01-02/2013 — www.TELE-audiovision.com

quired only if no DC power is provided from a receiver via one of the QUAD/QUAT-RO outputs. Any DC voltage from 10 V to 20 V is suitable for GTU. The unit consumes about 200 mA DC.

Finally, there are two LED indicators in the GTU: one for showing the presence of DC power, the other one to inform the user that a RF signal is available at the out-puts.

The workmanship of the devices is very good, they are robust and you should not have any problems with the installation if only you comply with the compre-hensive “QUAD and QUA-

Closeup of the measurement results at the input (left) and output (right) signal

Table 1. Test signals

TRO GTU Installation Guide” available from GlobalInva-com. Among other things, it also explains how to se-cure fibre optic cable. This is probably the most tricky part for anyone new to fibre optic cabling, so we advice you to read it carefully be-fore the installation.

Before we could meas-ure the performance of the GlobalInvacom system with

terrestrial signals we had to build a test setup. First, we connected a terrestrial TV antenna to a DTT headend. The headend’s job was to clean the input signal from unwanted components and after this to deliver it to the ODU32 Optical Transmitter. Since our DTT headend was able to manage three fre-quency channels, we start-ed the test with three DVB-T

multiplexes available in our location on these TV chan-nels: 41, 45 and 48. Table 1 lists the parameters of our test signals. (Table 1.)

We connected the output of the DTT headend to the ODU32 Optical Transmitter and the optical output of the ODU32 to the optical input of the QUAD GTU and meas-ured the signal at the input and at the output of the op-

DATATECHNICAL

Manufacturer GlobalInvacom Ltd., Great Britain

Web www.globalinvacom.com

E-mail Fibre@globalinvacom.com

Phone +44-1621-743440

Fax +44-1621-743676

Model QUAD GTU and QUATRO GTU

Function Light-to-RF converters with quad/quatro outputs

Satellite

Frequency range 950–2150 MHz

Gain variation across band 7 dB

Nominal output level 70 dBµV (QUAD) and 75 dBµV (QUATRO)

Terrestrial band rejection 30 dB

DTT, DAB and FM

Frequency range for DTT 470-862 MHz

Frequency range for DAB 174-240 MHz

Frequency range for FM 88-108 MHz

Nominal output power 68 dBµV

Gain variation across band 5 dB

Noise figure @ max. gain 6 dB

IF band rejection 20 dB

Optical

Optical wavelength 1100-1650 nm

Optical power -15 dBm to 0 dBm

DC

Voltage 10-20 V

Current consumption max. 220 mA @ 10 V (QUAD) 210 mA @ 10 V (QAUTRO)

Physical

Dimensions (without plastic) 109 x 136 x 50 mm

Jacek PawlowskiTELE-audiovision

Test CenterPoland

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www.TELE-audiovision.com/10/09/globalinvacomMORE ABOUT THIS COMPANy

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Output # Power C/N MERdBµV dB dB

1 70.9 32.8 23.72 70.8 32.6 23.53 70.7 32.4 23.54 70.5 32.5 23.4

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60 61TELE-audiovision International — The World‘s Largest Digital TV Trade Magazine — 01-02/2013 — www.TELE-audiovision.com www.TELE-audiovision.com — 01-02/2013 — TELE-audiovision International — 全球发行量最大的数字电视杂志

Very good noise performance – signal quality at the output is almost as good as at the inputAutomatic gain control works very wellAll Quad outputs are equally good in perfor-manceFlat characteristics over the entire UHF fre-quency bandSuitable for all standards of terrestrial signals: DTT/DAB/FM

None

Expert Opinion

it, we noticed that the pro-cessor degrades MER by a decibel or so. So, perhaps we could get even a better result without using the DTT processor and thus ignoring GlobalInvacom’s recom-mendation? Guess what, we tried it, but no – the results were even worse! Admit-tedly, without the DTT pro-cessor MER at the input to the optical system was bet-ter by 1 dB, but at the same time MER at the system out-put was worse by 0.7 dB.

How to explain this un-expected behaviour? By removing the DTT proces-sor we improved one input parameter (MER) but we degraded the ratio of use-ful signals to unwanted sig-nals including the noise in the whole terrestrial band. MER measurement is a nar-row band technique – only

one transmission channel is taken into account. It can not reveal the presence or absence of the signals or strong noise in the neigh-boring channels.

To sum it up, GlobalInva-com’s new QUAD and QUA-TRO GTUs in combination with their ODU32 Optical transmitter proved to be high performance compo-nents oftheir optical dis-tribution system. Despite of two signal conversions: from RF to light and back, signal quality was affected minimally while its power was increased.

To sum it up: GlobalInva-com’s fibre optic system is an excellent choice not only for the distribution of satel-lite signals but also for com-bined satellite and terres-trial signals via one single fibre optic cable.

ODU32 Input Output 1 of QUAD GTUChannel # Power C/N MER Power C/N MER

dBµV dB dB dBµV dB dB41 75.2 35.8 23.1 79.2 33.4 21.745 74.2 36.8 24.7 79.7 33.4 2448 70.6 33.5 21.7 79.2 33.6 21.6

Table. 2. Input and output of the optical system.

Output # Power C/N MERdBµV dB dB

1 80.7 33.9 23.62 80.1 34.2 23.53 80.1 34.1 23.54 80.5 33.8 23.8

Table 3. Results for channel 45 for all four outputs of QUAD GTU.

QUAD and QUATRO GTU de-vices respectively) while not degrading their quality and thus not improving terres-trial reception.

Thanks to the DTT head-end we were able to check the performance of the GlobalInvacom system for the lowest and highest DTT channels. We simply shifted channel 45 to channel 21 and later to channel 68 (474 and 850 MHz respectively). We got practically the same results as for the channel 45 located in the middle of the UHF band: Power = 79.2 / 76.2 dBµV, C/N = 33.6 / 32.3 dB and MER = 23.9 / 23.5

Before finishing our test, we decided to verify one of GlobalInvacom’s recom-mendations, namely the one for using a DTT processor before injecting a terres-

Table 4. Results for channel 45 for all four outputs of the QUAD GTU with the presence of satellite signal.

tical system. See the results in Table 2.

The signal at the output was stronger than that at the input and more uniform – we noticed only a 0.5 dB spread. This is the effect of the automatic gain control which is embedded in GTU converters. The carrier-to-noise was also very similar for all three channels. How-ever, we were most inter-ested in the MER readings as this parameters directly reflects signal quality. As you can see in Table 2, MER degradation was very limit-ed despite two conversions: from RF to light and back. Such conversion always de-teriorates signal quality but

fortunately in the GlobalIn-vacom system the changes in MER between input and output were really negligent - from 0.1 to 1.4 dB depend-ing on the channel.

Then, we checked if there are any significant differ-ences between the QUAD GTU outputs. See the re-

sults in Table 3. Practically all the outputs are identical.

All the measurements so far were made without a satellite signal. It was time to check if adding a satel-lite signal would have any impact on the terrestrial signal. We connected a GlobalInvacom optical LNB to the ODU32 and checked that the full spectrum of the IF satellite band is available at the outputs of the QUAD GTU. We repeated the measurements of terrestrial channel 45 on all four out-puts. Table 4 presents the results. You should compare them with the numbers in Table 3.

Table 4. Results for chan-nel 45 for all four outputs

the MER was unaffected. This means: the terrestrial signal quality was as good as in the test without satel-lite signal!

The same tests with the QUATRO GTU gave even better results. Without a satellite signal we had a channel power around 80 dBµV, C/N around 34.5 dB and MER around 24.3 and after adding the satellite signal, power decreased only to 75.5 dBµV while C/N and MER remained the same.

The conclusion is: the presence of a satellite sig-

of the QUAD GTU with the presence of satellite signal.

The output power de-creased by 10 dB but was till quite high – around 70 dBµV. But we were ex-tremely happy to notice that

nal in the optical system influences only the output power level of terrestrial signals (by 10 dB or 5 dB for

trial signal into the optical system. When we measured the terrestrial signal before the DTT processor and after